In the case of partial response (PR) equalization of a playback signal from an optical disc and so on as described in PTL 1, noise is also emphasized. NPML (Noise Predictive Maximum Likelihood) is known to improve detection capability by whitening emphasized noise.
Also, if a track pitch is narrowed to increase optical disc density, crosstalk from adjacent tracks will increase. For example, PTL 2 describes a crosstalk canceller that supplies respective playback signals of a target track to be played and tracks on both sides thereof to an adaptive equalizer so as to control a tap factor of the adaptive equalizer.